In refrigerated cargo ships carrying a general cargo, as opposed to containerized cargo, the general method of cooling the holds is essentially that each of the holds has a fan room or cooling room at one end. The holds are divided from each other by substantially air-tight decks. In the cooler rooms, there is a series of fan batteries which discharge air downwardly through cooling coils into a plenum chamber which extends substantially the full width of the ship. Cool air supply leaves the plenum chamber and enters the fore and aft passageways in the deck of the compartment with the supply of cooler air travelling from the fan room towards the opposite end of the hold. All along the length of the hold, the cooler air emerges from the deck through a series of perforations in the upper surface of the deck. The air flows upward through the cargo to the upper portion of the hold and then in the clear space above the cargo flows back to the fan room and through screened openings in the upper part of the fan room bulkhead and then back to the fans.
In all refrigerated (reefer) ship designs, the refrigerated decks generally incorporate a conventional structural concept for flat steel decks. These conventional decks have as their upper structural boundary a steel plate surface which is supported from below by an arrangement of fore and aft and transverse beams of varying depths. The longitudinal passageways for the chilled or cooled air are formed by fore and aft bearers on the upper surface of the steel plate deck. These bearers may be either steel or wood and they support a grating deck generally of perforated plywood. There are also some systems which utilize special aluminum sections to form both the bearers and the grating surface. However, in all of these systems, the bearers do not contribute to the structural strength of the deck or of the ship but serve only as spacers and supports between the steel deck surface and the grating deck. The reason that the decks employing even steel longitudinals cannot treat the longitudinals as strength members of the deck or of the hull is that the longitudinals are not supported by brackets along their length (since these would interfere with the required air flow) and are not considered to be adequately stable for use as structural members.
Therefore, it is an objective of this invention to overcome the inadequacies of the prior deck construction for refrigerated cargo ships by employing a folded steel plate which forms the deck membrane and extends longitudinally forming an alternate series of longitudinally-extending V-shaped channels and a series of inverted V-shaped longitudinally-extending channels through which V-shaped channels cool supply air may flow, and through which inverted V-shaped channels return air may flow.
It is a further objective of this deck construction to provide additional bending strength along the length of the folds and to provide added strength in the transverse direction and to break the span in the longitudinal direction by introducing trusses into the deck structure.
Yet a further objective of this invention is to incorporate a uniform depth to the entire deck structure with longitudinal and transverse members equal in depth and contained, in effect, within each other.
Furthermore, it is an objective of this invention to incorporate the members forming the structure of the deck to form also the air circulation channels.
Another objective and advantage of this deck construction is that the corrugations provide sufficient stiffness in bending to permit the corrugated plate to be viewed as a series of connected beams or girders. The deck construction provides a truss structure perpendicular to the length of the corrugations thereby furnishing the necessary stiffness and support required.
A further advantage of this invention is the ability to incorporate a truss structure within the overall depth of the corrugations by utilizing the corrugated plate itself with the requisite stiffness in the manner of the transverse truss to provide the lacing, or shear transmitting structure, necessary to permit the upper and lower flanges to act as an integrated truss resulting in a structure having a means of simply providing unobstructed longitudinal passages.